Method of on-site production of novel textile reinforced thermoplastic or thermoset pipes

ABSTRACT

Novel thermoplastic pipes which can withstand extremely high internally generated and/or applied pressures for utilization within, primarily, high pressure underground liquid and gas transport systems are provided. Such pipes are improvements over standard metal (i.e., steel, lead, and the like) pipes due to construction costs, shipping costs, implementation costs (particularly underground), modulus strength allowances to compensate for underground movements (i.e., earthquakes and tremors), non-rusting characteristics, and ease in manufacture. Such pipes are preferably reinforced with specific fabric articles which permit a lower thickness of plastic to be utilized than is generally required to withstand high pressure situations. A one-step, potentially on-site production method, is also contemplated within this invention.

FIELD OF THE INVENTION

The present invention generally relates to novel thermoplastic pipeswhich can withstand a varied range of internally generated and/orapplied pressures for utilization within, primarily, underground liquidand gas transport systems. Such pipes are improvements over standardmetal (i.e., steel, lead, and the like) pipes due to construction costs,shipping costs, implementation costs (particularly underground), modulusstrength allowances to compensate for underground movements (i.e.,earthquakes and tremors), non-rusting characteristics, and ease inmanufacture. Such pipes are preferably reinforced with specific fabricarticles that permit a lower thickness of plastic to be utilized than isgenerally required to withstand high pressure situations. A simplified,potentially on-site production method is also contemplated within thisinvention.

BACKGROUND OF THE INVENTION

Underground transport of liquids and gases has been utilized for manyyears. Such underground transport has proven to be the most efficientand safest manner in which to transport potentially explosive,flammable, and/or toxic liquids (such as crude oil, for example) andgases (such as methane and propane, as examples) long distances. Theprinciple method followed to provide such long distance undergroundtransport has been through metal tubes and pipes. In the past, theutilization of metals (such as steel, copper, lead, and the like) waseffective from cost and raw material supply perspectives. However, withthe population growing throughout the world and the necessity fortransporting liquids and gases to more remote locations increases, thecontinued utilization of such metal articles has become more and moredifficult for a number of reasons. Initially, the production of suchmetal tubes and pipes must be undertaken through high-temperatureproduction methods at specific foundries which are normally located asubstantial distance from the desired installation site. Such off-siteproduction thus requires transport of cumbersome metal articles to theinstallation location and then subsequent placement into already-dugchannels. These procedures are, again, difficult to follow since metalarticles are rather heavy and must be connected together to form thedesired pipeline. Additionally, in order to reduce the number ofconnections between individual pipes, longer metal pipes could beformed, which adds to the complexity with an increase in required weldedconnections. Further problems associated with metal pipes and tubesinclude, without limitation, the potential for rusting (which maycontaminate the transported liquid or gas), the low threshold ofearth-shifting which could cause a break within the pipeline, and thedifficulty in replacing worn out metal pipes in sections, again due tothe metal pipe weight, metal pipe length, and connection welds. Thesebreak problems have proven to be extremely troublesome in certaingeographic areas which are susceptible to earthquakes and tremors on aregular basis. When such unexpected quakes have occurred in the past,the metal gas and liquid pipelines have not proven to be flexible enoughto withstand the shear forces applied thereto and explosions, leaks, ordiscontinued supplies to such areas have resulted. These metal articleshave remained in use because of their ability to withstand highpressures. Furthermore, although such metal pipes are designed towithstand such high pressures (i.e., above 80 bars, for instance), oncea crack develops within the actual metal pipe structure, it has beenfound that such cracks easily propagate and spread in size and possiblynumber upon the application of continued high pressure to the sameweakened area. In such an instance, failure of the pipe is thereforeimminent unless closure is effectuated and repairs or replacements areundertaken.

Although there is a need to produce new pipelines to remote locationsaround the world, there is also a need to replace the now-deterioratingpipelines already in use. Aging pipelines have recently caused greatconcern as to the safety of utilizing such old articles. Unexpectedexplosions have occurred with tragic consequences. Thorough review andreplacement of such old metal pipes is thus necessary; however, due tothe difficulties in determining the exact sections of such pipelineswhich require replacement, there is a desire to completely replace oldpipelines but following the same exact routes. Again, due to thedifficulties noted above, there is a perceived need to develop morereasonable, safer, longer-lasting, easier-to-install, non-rusting,non-crack propagating, and more flexible pipeline materials. To date,there have been some new thermoset or thermoplastic articles which aredesigned to withstand rather low pressure applications (i.e., 20 bars orbelow) and which include certain fiber-wound reinforcement materials(including fiberglass, polyaramids, polyesters, polyamides, carbonfibers, and the like). However, the resultant articles do not includespecific textile reinforcements (they are fibers wound around specificlayers of plastic material) and thus are difficult and rather costly toproduce. Furthermore, such fiber-wound materials cannot be easilyproduced at the pipe installation site again due to the complexity ofcreating fiber-wound reinforcement articles subsequent to thermoplasticor thermoset layer production. Additionally, with such off-siteproduction, transport and in-ground placement remain a difficultproblem. Thus, although some improvements have been provided in the pastin relation and in comparison to metal pipes and tubes, there simply isno viable alternative presented to date within the pertinent prior artwhich accords the underground liquid and gas transport industry a mannerof replacing such high pressure metal articles.

OBJECTS OF THE INVENTION

It is thus an object of this invention to provide such a viablealternative method for replacing or overcoming the shortcomings anddifficulties of high pressure (i.e., from about 20 to about 100 bars)underground metal pipes and tubes. Another object of this invention isto provide a suitable fabric reinforcement system which permits arelatively low amount of thermoplastic or thermoset composition to beutilized in order to produce a pressure-resistant thermoplastic pipearticle. Yet another object of this invention is to provide aninterlocking mechanism to best ensure the textile reinforcement layerremains in place during and after introduction of the outerthermoplastic or thermoset layer. Still another object of this inventionis to provide a suitable simplified method of producing such atextile-reinforced thermoplastic pipe article.

SUMMARY AND BRIEF DESCRIPTION OF THE INVENTION

Accordingly, this invention encompasses a pipe comprising at least twodistinct layers of thermally manipulated polymeric material and at leastone layer of textile reinforcement material, wherein said textilereinforcement material is sandwiched between said two distinct layers ofsaid thermally manipulated polymeric material, wherein the elongation atbreak exhibited by such a pipe is limited solely to the elongation atbreak exhibited by said textile reinforcement material, and wherein saidtextile reinforcement material exhibits an elongation at break of atmost 20%, preferably at most 15%, more preferably at most 10%, and mostpreferably at most 6%. Preferably said pipe is constructed to withstandat least 100 bars of internal pressure before exceeding the elongationat break limit. An alternative yet also preferred embodiment is a pipewhich exhibits at most 20 bars of pressure of internal pressure beforeexceeding the elongation at break limit and a wall thickness of saidpolymeric material of at most 1/11th of the diameter of said pipe,preferably at most about 1/15^(th), more preferably at most about 1/20,and most preferably at most about 1/25th. Also contemplated within thisinvention is the pipe as noted above wherein the textile reinforcementmaterial introduced within said pipe is a flat structure having a firstside and a second side which is formed into a tubular structure aroundthe inner polymeric layer upon overlapping contact of said first andsecond sides and which possesses means to adhere or interlock saidoverlapped first and second sides.

The term “thermally manipulated polymeric material” is intended toencompass the well known polymeric compositions of a) thermoplastics andb) thermosets. Such terms are well known and describe a) any syntheticpolymeric material that exhibits a modification in physical state fromsolid to liquid upon exposure to sufficiently high temperatures and b)any synthetic polymeric material that exhibits orientation in apreselected configuration upon exposure to sufficiently hightemperatures. Most notable of the preferred thermoplastic types ofmaterials are polyolefins (i.e., polypropylene, polyethylene, and thelike), polyester (i.e., polyethylene terephthalate, and the like),polyamides (i.e., nylon-1,1, nylon-1,2, nylon-6 or nylon-6,6), andpolyvinyl halides (i.e., polyvinyl chloride and polyvinyl difluoride, asmerely examples). Preferred within this invention are polyolefins, andmost preferred is polypropylene. Such materials are generally petroleumbyproducts and are readily available worldwide. These materials areproduced through the polymerization of similar or different monomersfollowed by the melt extrusion of the polymerized materials in pelletform into the desired shape or configuration. Upon solidificationthrough cooling, such materials exhibit extremely high pressureresistance, particularly upon introduction of nucleating agents, such assubstituted or unsubstituted dibenzylidene sorbitols, available fromMilliken & Company under the tradename Millad®, and/or certain sodiumorganic salts, available form Asahi Denka under the tradename NA-11™.Such nucleating agents are either mixed and provided within thepelletized polymers, or admixed within the melted polymer compositionprior to extrusion. These compounds provide strength enhancements andaccelerate thermoplastic production by producing crystalline networkswithin the final thermoplastic product upon cooling at relatively hightemperatures. Theoretically, at least, with a stronger initialthermoplastic product, the more durable and potentially longerfunctional lifetime provided by such a product. Preferred thermosetmaterials include materials such as polyurethane, polycarbonate, or thelike.

Since pipe diameters utilized for largescale underground transportapplications are generally measured in feet rather than inches ormillimeters, the wall thicknesses required to provide the desired highpressure characteristics are extremely high for thermoplastics orthermosets alone. Although such thermoplastic and/or thermoset materialsprovide certain pressure resistances, in general the wall thicknessrequired to withstand pressures of about 80 bars requires a standarddiameter to wall thickness ratio of at most 11:1 (for polyethylene forexample). Thus, in order to provide such high pressure characteristicswithout exceeding the elongation at break limits of the polymericmaterials present in pipe form (i.e, substantially cylindrical), withpipe diameter of, for example, about 232 millimeters (about 9 inches),the wall thickness of the pipe must be at least about 21 millimeters, orabout 0.85 inches) to withstand such high pressures. Even with suchthick walls, the polymeric materials would not provide any resistance tocrack propagation should a weakened area of the pipe produce such aburst point. There is a strong desire to increase the pressureresistance (and thus consequently, the elongation at breakcharacterstics) of the target polymeric pipe material in order either toprovide much thinner wall thicknesses without a loss in pressureresistance as compared with the standard polymeric materials alone, orto provide greater pressure resistant thick-walled pipes which are morereliable upon exposure to very high pressure situations. Such desirablebenefits have been unavailable through practice of a relatively simplemanufacturing method with actual textile reinforcement materialsproviding the basis of pressure resistance for the entire pipe article.

Apparently, upon application of internal pressure within suchnon-reinforced thermoplastic and/or thermoset piping materials, thematerials expand in the direction dictated by the pressure thereforethinning the wall thickness either to the point of breaking (i.e., tothe elongation at break limit) or until the pressure is discontinued.After discontinuing the pressure, however, the pipe walls do not returnto their original thicknesses. Also, if the pressure is appliedunevenly, or if there is a discrete area within the thermoplastic orthermoset pipe wall which is already thinner than the other areas, thenthe pipe will more easily burst in relation to the pressure buildup orin relation to the thinner wall portion. In order to alleviate suchdetrimental expansion and burst possibilities within thermoplasticpiping materials, reinforcing materials have been developed tocompensate for such problems. However, in the past, such pipingmaterials have been limited primarily to hoses and short tubes (i.e.,automobile tubing) which did not require the ability to withstandextremely high pressures.

It has now been found that the incorporation of certain textilereinforcement materials permit reduction of the diameter to wallthickness ratio for standard thermoplastic and/or thermoset materials byat least a factor of 1.5 (a ratio for any thermoplastic of at the most1:17 in order to withstand a pressure of at least 80 bars). Preferably,then, the thickness of the inventive pipe walls should be no greaterthan about 1/17^(th) of the pipe diameter; more preferably no more thanabout 1/20^(th), and most preferably no greater than about 1/25^(th) ofthe pipe diameter. The term “withstand pressure” is intended toencompass the ability to prevent elongation of the entire pipe materialto a point of breaking or weakening in discrete areas (i.e., thinning ofcertain areas to permit leakage). Such ability to withstand pressure isimperative since the utilization of high pressures internally provides aconsistent and continuous force seeking equilibrium with the externalpressures. Any excess thinning of the pipe material would therefore mostlikely result in bursting of the pipe due to physical requirements ofequaling pressures. Such textile reinforcement materials thus aid in thereduction of elongation of the thermoplastic or thermoset pipecomponents upon application of high pressures therein. As notedpreviously, it has been determined that the elongation at break of suchtextile reinforcements provides the overall elongation at breakexhibited by the target pipe article, particularly upon the presence ofsuch reinforcement materials between at least two distinct layers ofthermoplastic or thermoset materials. In such a manner, the entirearticle relies primarily upon at least one textile reinforcement layerto provide the desired high elongation at break limit and the low crackpropagation exhibited by the reinforced thermoplastic or thermosetmaterial. Furthermore, such a reinforcement material also aids inproviding an increased tear resistance to the overall pipe article whichaids in reducing the chances of a breach in structural integrity as aresult of external shear force application (i.e., earth tremors, and thelike). Since there is strict reliance upon such properties exhibited andprovided by the textile reinforcement layer, the amount of thermoplasticor thermoset materials can be substantially reduced with no reduction inreliability under pressurized situations. Also, if so desired, the usermay still utilize a substantial amount of thermoplastic or thermosetmaterial in combination with the sandwiched textile reinforcement layeror layers with confidence that, again, the inventive pipe article willexhibit improved and reliable pressure resistance, crack propagationresistance, and tear resistance.

Of enormous importance in this instance is the flexibility exhibited bythe inventive pipes when subjected to external shear forces, for exampleearth tremors, and the like. Such flexibility permits the pipes toexhibit some movement in relation to the shear forces generated by suchexternal occurrences. In the past, as noted above, metal pipes sufferedfrom the lack of flexibility in that the application of such externalshear forces would result in the burst of certain pipes due to suchexternal forces exceeding the shear force threshold possessed by themetal materials. Such flexibility is most suitably measured in terms oftear resistance to the overall pipe article. In general, metal pipesexhibit at most a tear resistance of about 6% (copper exhibits thehighest such tear resistance), which is extremely low when the potentialfor very strong shear forces underground are significant (particularlyin certain parts of the world prone to earth tremors, earthquakes, andthe like). The thermoplastics and/or thermosets provide initial tearresistance measurements in excess of at least 20%, with a potential highmeasurement of more than about 100%, particularly upon incorporation ofthe sandwiched textile reinforcement material as discussed above. Thus,the inventive pipes should be able to withstand enormous shear forces,at least better than metal pipes, due to their exhibited tear resistanceand thus flexibility characteristics.

As noted above, at least two layers of such thermoplastic and/orthermoset materials are present within the inventive thermoplasticand/or thermoset pipes. These layers are separated, at least in part, bya textile reinforcement material. The total wall thickness of theinventive pipe, as noted above, is dependent upon the discretion of theproducer and in relation to the properties provided by the textilereinforcement layer itself. If a thin-walled, low pressure pipe isdesired, then the typical wall thickness may be anywhere from about 4 toabout 15 millimeters. A higher elongation at break characteristicexhibited by the textile reinforcement permits lower thicknesses to beutilized. Such elongation at break characteristics are generallymeasured by the amount of force such textile reinforcements maywithstand. Thus, a textile exhibiting at least an elongation at break ofabout 2-3% (i.e., similar to that exhibited by steel but greater thanfor most thermoplastic and/or thermoset compositions) is desired. Ofcourse, textile materials exhibiting far in excess of this elongation atbreak minimum are more preferred, with no real maximum level, only thatwhich may deleteriously affect the overall stiffness of the product,thereby potentially providing tear resistance problems. The elongationat break level for preferred textile reinforcements is determined by anumber of factors, including the tenacity of the constiruent fiberswithin the textile (a higher dtex provides a stronger textile overall),the angle of contactin relation to the direction of the pipe (angles ofform 40 to 70° are preferred, while specific angles of between 45 and65° and 50 and 55° are more preferred, respectively. An angle ofspecifically 54° 44′ has been found to provide the greatest overallstrength to the target pipe article. Thicker layers of textilereinforcement material also appear to provide stronger overall products,as do scrim and in-laid textiles.

The term “textile reinforcement material” or “textile reinforcement” or“textile reinforcement layer” simply requires a combination ofindividual yarns or fibers in a configuration which is an integratedtwo-dimensional article prior to incorporation between the at least twolayers of thermally manipulated polymeric materials. Thus, wound stripsincorporated over a completed inner layer is not encompassed within sucha definition. Nor are fiber-containing tape articles which are alsowound around a formed polymeric pipe article. The specific textilereinforcement materials may be of any particular configuration, shape,and composition. The inventive textile reinforcements are present as atleast a single layer of material with a total aggregate thickness of atleast about 500 microns, preferably at least about 400 microns, morepreferably at least about 300, and most preferably up to about 300microns. Such textiles preferably exhibit a mesh structure between thetwo layers of thermoplastic and/or thermoset materials. In general, itis highly desired that synthetic fibers, either alone, or in conjunctionwith metal threads, be utilized within the reinforcement materials. Suchsynthetics are less likely to be susceptible to deterioration over timedue to potential presence of bacteria, moisture, salts, and the like,within and around the pipes as they would be positioned underground.However, with the proper precautions of proper coating, finishing, andthe like, natural fibers may serve this purpose as well. The preferredtextile reinforcements may be knit, scrim, woven, non-woven, in-laid,and the like, in form, with scrim and in-laid textiles most preferred.Such forms are most easily produced and maneuvered during the actualpipe production procedure. With in-laid textiles, at least two layersare desired to have one layer oriented at one angle and the other itscomplement in relation to the direction of the target thermoplasticpipe. Thus, one layer would be placed with all yarns and/or fibersoriented at an angle of about 54° 44′ to the pipe direction, the otheroriented at an angle of about −54′ 44′. In order to more easily holdsuch in-laid fabric layers in place, a thermoplastic film may be appliedeither between or on top of one or both layers. Such a film ispreferably extremely thin (i.e., less than about 200 microns, preferablyless than 100 microns, and most preferably less than about 50 microns)and, being a thermoplastic, will easily react with the outer layer ofthermoplastic upon heating and molding around the inner layer/fabricreinforcement composite. Alternatively, sewn threads may be utilized tohold such multiple layers in place prior to, during, and after pipeproduction.

The yarns within the specific textile reinforcement materials may beeither of multifilament or monofilament and preferably possess arelatively high dtex, again, to provide the desired tenacity andstrength to the overall pipe article. A range of decitex of from about200 to about 24,000 is therefore acceptable. Mixtures of such individualfibers may be utilized as well as long as the elongation at break of thecomplete textile reinforcement material dictates the elongation at breakfor the complete thermoplastic and/or thermoset article. Multifilamentfibers are preferred since they provides better adhesive properties andgreater overall strength to the textile. The individual fibers may be ofpolyester, polyamide, polyaramid, polyimide, carbon, fiberglass(silicon-based, for example), boron-derivative, and possibly,polyolefin, in nature. Again, natural fibers, such as cotton, wool,hemp, and the like, may be utilized but are not as trustworthy as thesynthetic types listed above. Due to high processing temperaturesassociated with polymeric pipe extruding, it is highly desirable toavoid the sole utilization of low melting-point polyolefin yarns.However, a plurality of individual fibers of such polyolefins (i.e.,polypropylene, polyethylene, and the like) may be utilized incombination with the other synthetic fibers in order to improve adhesionupon melting of such yarns upon exposure to the higher temperaturespresent during the contacting of the textile reinforcement to thethermoplastic and/or thermoset inner and outer layers. Fiberglass andboron-derivatives are preferred due to their strength characteristicsand their alkaline resistance. The remaining fibers are also acceptable,including, most prominently, polyaramids, polyimides, carbon fibers, andpolyesters. Polyesters are desirable from a cost standpoint while theremaining fibers are excellent with regards to strength.

Of particular preference within this invention are yarns of core-sheathtypes, as taught within U.S. Pat. No. 5,691,030 to DeMeyer, hereinentirely incorporated by reference. Such specific yarns permit breakageof the sheath components without affecting the strength of the corefilaments therein. Such core filaments may be monofilament syntheticfibers (such as polyester, polyamides, polyaramids, polyolefins, and thelike), although, in one potentially preferred embodiment, at least aportion of such core filaments are metallic in nature (such as,preferably, copper, silver, gold, and the like) in order to permitconduction of electrical current and/or heat over the entire pipeline.Such metal threads, fibers, yarns, etc., are not limited to being corefilaments and thus may be present as distinct in-laid, woven, knit,no-woven, placed, scrim, components.

Such metallic components provide great strength as needed within thefabric reinforcement materials; however, they also may serve to provideother highly desirable benefits for both the inventive pipes and theoverall pipeline comprising such pipes. For example, such conductivecomponents may permit the introduction of a low electrical current overthe entire pipeline (through a continuous connection of metalcomponents) or through certain segments thereof. In such a manner, adetection system may be implemented to determine where and at what timea pipe has burst or a leak is present. Upon interruption of the desiredelectrical signal (i.e., the specific amps of current), a valve may beoperated to close off a certain portion of the pipeline until repairsare made. Such a system merely requires the connection of an ampmeter tothe pipeline and integration of a valve in relation to the measuredamperage flowing through the pipeline itself. Furthermore, with such adetection system, the ability to detect such problems from above-groundwould be provided as well as a signal in relation to a low amperagecount can be produced thereby signifying the specific location of theproblem. Such a method thus facilitates detection and replacement ofsuch thermoplastic pipes.

Additionally, in certain locations freezing temperatures may providedifficulty in transporting certain gases and liquids underground withoutthe ability to provide heated pipes. The presence of metal yarns, etc.,facilitates the generation of heat, potentially, within the desiredpipes with, again, the introduction of certain selected amounts ofcurrent and/or heat over the metal components. The heat generatedthereby may be utilized to effectively keep the desired pipes fromfreezing thereby permitting continuous transport therethrough.

Even upon utilization of a fabric reinforcement material configured atthe preferred angles noted above in relation to the pipe direction(i.e., 40 to 70°, most preferably 55°), the addition of a cross-yamwithin each repeating design, stitch, pattern, etc., configured at anangle of 0° in relation to the pipe direction is highly desired. Such across-yam permits melting of the entire pipe structure at discreteplaces in order to allow for curvatures to be introduced within thepipeline without deleteriously affecting the strength of the remainingfabric reinforcement material or compromising the shear strength of theentire pipe composite, particularly at the specific bent place. Such animprovement again shows the benefits of thermoplastic high pressurepipes since such curvatures may be produced at any angle and on-site onan as needed basis. Historically utilized metal pipes required formationof necessary curvatures at the foundry; if the angle of curvature wasincorrect, new parts had to be produced to compensate for such amistake. The inventive pipes permit on-site corrections if necessary.

It is desirable that the fabric reinforcement materials are in mesh formand thus exhibit open spaces between the constituent fibers and/or yarnstherein. Such open space should be large enough to permit a portion ofthe heated liquid outer thermoplastic layer to adhere to the alreadyformed inner thermoplastic layer therethrough and after cooling of theouter layer. In such a manner, not only is the three layer pipestronger, the reinforcement materials are better held in place. Althoughlarger open spaces between constituent fibers and/or yarns arepreferred, the only requirement is that at least a portion of the outerlayer exhibit some ability to adhere with the surface of the inner layerin contact with the fabric reinforcement materials. Thus, a range ofpreferred open space between individual constituent yarns of an area aslow as 0.001 square millimeters and as high as about 1 square centimeteris desired.

The separate polymeric material layers and textile reinforcement layermay comprise any number of additives for standard purposes, such asantimicrobial agents, colorants, antistatic compounds, and the like.Such antimicrobial agents would potentially protect the inner liningfrom colonization of unwanted and potentially dangerous bacteria (whichcould potentially create greater pressure within the pipes if a propernutrition source is present). Preferably, such an antimicrobial agentwould be inorganic in nature and relatively easy to introduce within thethermoplastic compositions within the pipe. Thus, silver-basedion-exchange compounds (such as ALPHASAN®, available from Milliken &Company, and other types, such as silver zeolites, and the like) arepreferred for this purpose. Colorants may be utilized to easilydistinguish the thermoplastic layers for identification purposes. Anypigment, polymeric colorant, dye, or dyestuff which is normally utilizedfor such a purpose may be utilized in this respect for this invention.Antistatic compounds, such as quaternary ammonium compounds, and thelike, permit static charge dissipation within the desired thermoplasticmaterials in order to reduce the chances of instantaneous sparkproduction which could theoretically ignite certain transported gasesand/or liquids. Although the chances of such spark ignition areextremely low, such an additive may be necessary to aid in this respect.

Such fabric reinforcement materials provide the aforementionedresistance to expansion, swelling, and/or burst due to the applicationof extremely high internal pressures within the target thermoplasticpipe material. Preferably, the fabric reinforcement material isconfigured at an angle of about 55° (54° 44′) in relation to thedirection of the target pipe itself. In such a manner, the fabricprovides the best overall strength and thus resistance to internalpressures due to its resistance to shear forces generated by theinternal pressure within the pipe. Depending on the amount of fabricutilized, however, the angle of contact may be as low as 0° and as highas 90°. With an angle configured in the same direction as the pipeitself, there is a higher risk of pipe burst due to the low shear forcethreshold provided by the fabric. Thicker fabrics may compensate forsuch shear force problems; however, the actual angle of contact shouldbe from about 40 to about 70°, with the particular 54° 44′ angle mostpreferred. Furthermore, the number of fabric layers utilized may beplural to provide greater reinforcement strength. In such an instance,it is highly desirable that contacting layers of fabrics be configuredat opposite angles of contact in relation to the pipe direction toaccord, again, the strongest reinforcement possible. The utilization ofa supplemental textile reinforcement layer oriented at an angle ofcontact with the pipe direction of either 0 or 90° imparts certaindesirable properties to the overall pipe article. Most notably, crushresistance is provided to ready-made pipes which are necessarily woundon a creel for transport to an installation site. A 0° reinforcementangle provides the best stiffness to compensate for the weight generatedby rolled pipes. Also, should an initial production of the inner layerbe desired in roll form, the incorporation of such a 0° textilereinforcement component may alleviate crushing problems associated withsuch storage and transport. A 90° orientation improves upon the tearresistance of the final product.

Although only two specific layers of thermoplastic and/or thermosetmaterials are required, it is to be understood that more than two suchlayers are acceptable within this invention. Such additional layers maybe of any type (and not necessarily thermoplastic and/or thermoset),including, without limitation, metal, ceramic, glass-filled plastic,rubber, and the like.

Other alternatives to this inventive article will be apparent uponreview of the preferred embodiments within the drawings as discussedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 shows an embodiment of the present invention illustrated as thepipe 10;

FIG. 2 shows a cross-section of the pipe 10 from FIG. 1;

FIG. 3 shows a partial cross-sectional view of an apparatus for formingthe pipe from FIG. 1;

FIGS. 4A-H illustrate cross-sectional views of the apparatus and pipefrom FIG. 3, illustrating the method of joining a reinforcing fabricwith an inner wall;

FIG. 5 illustrates a partial view of a textile for use in forming thepipe from FIG. 1 with the apparatus in FIG. 3;

FIG. 6 illustrates a textile for use as the reinforcing fabric forforming the pipe from FIG. 1 with the apparatus in FIG. 3; and

FIG. 7 illustrates an apparatus for the in situ formation and placementof the pipe from FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to potentially preferredembodiments of the invention, examples of which have been illustrated inthe accompanying drawings. It is to be understood that these are in noway intended to limit the invention to such illustrated and describedembodiments. On the contrary, it is intended to cover all alternatives,modifications and equivalents as may be included within the true spiritand scope of the invention as defined by the appended claims andequivalents thereto.

Referring now to the figures, and in particular to FIGS. 1 and 2, thereis shown a pipe 10 illustrating one embodiment of the present invention.The pipe 10 generally includes an inner wall 110, a reinforcing textile120, and an outer wall 130. The inner wall 110 is preferably formed of athermoplastic material, and has an inner passage surface 111 and aninner wall textile interface zone 113. The inner passage surface 111defines the interior of the pipe 10. The outer wall 130 is preferablyformed of a thermoplastic material, and has an outer surface 133 and anouter wall textile interface zone 131. The reinforcing textile 120 wrapsaround the inner wall 110 and engages the inner wall textile interfacesurface 133. The reinforcing textile 120 has a sufficient width tosurround the inner wall 110, and have textile overlap sections 121 wherethe edges of the reinforcing material overlap around the inner wall 110.A textile locking system 123 is employed between the textile overlapsections 121 to prevent the ends of the reinforcing material 120 fromseparating. The outer wall textile interface surface 131 engages thereinforcing textile 120 and the outer wall surrounds the reinforcingtextile 120. Such a textile locking system 123 may alternativelycomprise an adhesive composition (such as, as merely example,heat-activated or pressure-activated adhesives) which permits a secure,long-term connection between the overlap sections 121 and thus preventsseparation of the two sections upon pipe production and potentialelongation caused by high internal pressures.

Referring now to FIG. 3, there is shown a cross section of an apparatus200 for forming the pipe 10 in FIGS. 1 and 2. The apparatus 200generally includes an inner wall die 210, a mandrel 220, a reinforcingtextile guide 230, and an outer wall die 240. The inner wall die 210 hasan inner wall die aperture 211. The mandrel 220 extends through theinner wall die aperture 211 and includes an outer surface 221 forforming the inner passage 111 of the pipe 10 and providing support tothe inner wall 110 during the formation of the pipe 10.

Still referring to FIG. 3, the reinforcing textile guide 230 ispositioned around the mandrel 220 after the inner wall die 210. Thereinforcing textile guide 230 includes an inside textile guide 231 andan outside textile guide 232 for guiding the edges of the reinforcingtextile 120 to position the reinforcing textile 120 around the innerwall 110. In one embodiment of the apparatus 200, the reinforcingtextile guide 230 includes a joint material injector 235 that is locatedto insert a material between the overlap textile sections 121. In yetanother preferred embodiment, the reinforcing textile guide 230 includesa closing roller 237 that presses the overlapping portions of thereinforcing textile 120 together.

Referring still to FIG. 3, the outer wall die 240 is located around themandrel 220 and includes an inside die wall 241 and an outside die wall245. The inside die wall 241 of the outer wall die 240 includes aninside die wall aperture 242 to receive the inner wall 110 andreinforcing textile 120 combination. The inside die wall aperture 242has an inside die wall aperture taper 243 for assisting the inner wall110 and reinforcing textile 120 combination to transition into the outerwall die 240. The outer wall die 240 also has an outside die wall 245with an outside wall die aperture 246. A passage 223 in the mandrel 220provides air pressure to the inside of the pipe 10 at a point after theouter wall die 240 forms the outer wall 130 on the pipe 10. A connectingchain 225 secures a plug 224 inside the pipe 10 seals to the mandrel 220in order to maintain the pressure from the mandrel 220 within the pipe10.

Referring now to FIGS. 1, 2, and 3, in operation, a thermoplasticmaterial is extruded through the inner wall die aperture 211 onto theouter surface 221 of the mandrel 220 to form the inner wall 110 of thepipe 10. The outer surface of the mandrel 220 provides support to theinner wall 110 of the pipe 10 during the processes of applying thereinforcing textile 120 and the outer wall 130. After the inner wall 110has been extruded onto the mandrel 220, the reinforcing textile guide230 positions the reinforcing textile 120 onto the inner wall textileinterface zone 113.

Referring now referring to FIGS. 3 and 4A-H, the inside textile guide231 and the outside textile guide 232 guide opposing ends of thereinforcing textile 120 as the reinforcing textile 120 is positionedonto the inner wall textile interface zone 113. FIGS. 4A-H illustratethe sequence of how the reinforcing textile guide 230 apply thereinforcing textile 120 onto the inner wall textile interface zone 113of the inner wall 110 in a sequential manner. The inside textile guide231 first applies one edge of the reinforcing textile 120 to the innerwall 110 of the pipe 10. As the inner wall 110 of the pipe 10 progressesalong the extruding apparatus 20, the outside textile guide 232continues to wrap the reinforcing textile 120 around the textileinterface zone 113 of the inner wall 110. In this manner, thereinforcing textile 120 surrounds the inner pipe 110 in a way thatreduces the possibility of wrinkles in the reinforcing textile 120 orair pockets between the inner wall 110 and the reinforcing textile 120.

Still referring to FIGS. 3 and 4A-H, in one embodiment a textile lockingsystem 123, in the form of a joint material 123 a, is employed betweenthe textile overlap sections 121 of the reinforcing textile 120 toassist the reinforcing textile 120 to remain locked in an overlapposition when the finished pipe 10 is subjected to internal pressures.The joint material 123 a is injected between the textile overlapsections 121 by the joint material injector 235 just prior to theposition that the outside textile guide 232 joins together the textileoverlap sections 121. The joint material 123 a can be the same type ofmaterial that is used to form the inner wall 110, the outer wall 130, ora different material selected to help secure the textile overlapsections 121 from separating. In another embodiment, the joint material123 a is a tape, ribbon, strand, or the like that is placed intoposition between the textile overlap sections 121 prior to the textileguide 230 joining together the textile overlap sections 121.

In an alternative yet preferred embodiment, the textile locking system123 is a mechanical locking system utilizing mechanical devices such ashooks, piles, or other mechanical mechanisms. In a version of thetextile locking system incorporating hook devices, a plurality of hookdevices extending up from the lower textile overlap section 121 into theupper textile overlap section 121, down from the upper textile overlapsection 121 into the lower textile overlap system, or both. The textilelocking system 123 using hook devices can use hook devices similar tothe hook devices in a hook and pile closure system. In a version of thetextile locking system 123 that employs a pile type element, the piletype element can extend from the lower textile overlap section 121 intothe upper textile overlap section 121, from the upper textile overlapsection 121 into the lower textile overlap section 121, or both. Thetextile locking system 123 using a pile type element can have a piletype element formed from the same fibers or yarns of the reinforcingmaterial, and can also have the pile elements canted to angle backtowards the center of the reinforcing textile 120. In anotherembodiment, the textile locking system 123 employing a mechanical devicecan incorporate the mechanical device onto a ribbon, strip, strand, orthe like that is placed into position between the textile overlapsections 121 prior to the textile guide 230 joining together the textileoverlap sections 121. The textile locking system 123 employing amechanical device in the form of a ribbon, strip, strand, or the like,the locking system 123 can also be positioned below the lower textileoverlap section 121 and extend up into both textile overlap sections121, or above the upper textile overlap section 121 and extend down intoboth textile overlap sections 121. Additionally the textile lockingsystem can employ both the joint material 123 a and the mechanicalsystems described above.

Referring back now to FIG. 3, once the textile locking system 123 islocated in place, the closing roller 237 presses the textile overlapsections 121 together in preparation for applying the outer wall 130.The outer wall 130 is formed around the inner wall 110 and reinforcingtextile 120 combination by the outer wall die 240. The inner wall 110and reinforcing textile 120 combination enters the outer wall die 240through the inside wall aperture 242 of the outer wall die 240. Theinside wall aperture taper 243 assists the inner wall 110 andreinforcing textile 120 combination transition into the outer wall die240. A thermoplastic material is extruded into the outer wall die 240and surrounds the inner wall 110 and reinforcing textile 120combination. The inner wall 110, reinforcing textile 120, and outer wall130 exit the outer wall die 240 through the outside die wall aperture246 in the outside die wall 245. The outside wall die 240 is illustratedin FIG. 3 as being perpendicular to the pipe 10; however, it iscontemplated that the outside wall die 240 can be at an angle such thatthe inside wall a inside die wall 241 and the outside die wall 245 forman acute angle to the inner wall 110 and reinforcing textile 120combination entering the outer wall die 240. This acute anglefacilitates the forming of the outer wall 130 on the pipe 10 and helpsreduce the tendency of the thermoplastic material to leak out of theinside die wall aperture 242.

Still referring to FIG. 3, air pressure applied to the passage 223 inthe mandrel 220 exits into the interior of the pipe 10 after the outerwall 130 has been formed. The plug 225 inside the pipe 10 helps retainthe pressure inside the pipe 10. A connecting chain 227 holds the plug225 adjacent to the mandrel 220. The pressure applied within the pipe 10prevents collapse of the entire structure as the three layer pipe 10hardens into its final shape. After hardening, the plug 225 is removedand the resulting pipe structure 10 is ready for utilization in tandemwith other such pipes (not illustrated) as an entire high pressurepipeline (not illustrated).

Referring now to FIG. 5, there is shown a partial view of a textile 300for use as the reinforcing textile 110 illustrated in FIGS. 1 and 2. Thetextile 300 includes electrode elements 311 and 312, and resistiveelements 320. As illustrated in FIG. 5, the electrode elements 311 and312 are conductive materials that run parallel along the length of thetextile 300 as the selvage yarns. The resistive elements 320 are wovenaround the electrode elements 311 and 312, and interlaced to form afabric. As an example, the resistive elements 320 can be a yarn formedof a flexible core having a fine resistance wire or tape wound spirallythereon, or having a layer of carbon particles bonded thereon by athermoplastic or resin binder. The electrode elements 311 and 312, andthe resistive elements 320 are flexible to form a fabric that can beplaced around the inner wall 110 as the reinforcing fabric 120illustrated in FIGS. 1 and 2.

Referring now to FIGS. 1-2 and 5, by using the textile 300 in FIG. 5 asthe reinforcing fabric 120 in FIGS. 1 and 2, an electrical current canbe applied to the electrode elements 311 and 312 of the fabric 300 whenin place within the pipe 10. The electrical current supplied to theelectrode elements 311 and 312 passes through the resistive elements 320and generates heat. In this manner, the pipe 10 can be used to applyheat to the contents of the pipe 10, or to compensate for the loss ofthermal energy from the contents of the pipe 10 to the exterior of thepipe.

Referring now to FIG. 6, there is shown another embodiment of a textile400 for use as the reinforcing textile 120 of the pipe 10 in FIGS. 1 and2. The fabric 400 generally comprises selvage yarns 430, electrode yarns411 and 412, and resistive yarns 420. The electrode yarns 411 and 412are woven around the selvage yarns 430 such that a resistive yarn 420separates each electrode yarn 411 and 412. At each intersection of theelectrode yarns 411 and 412, the electrode yarns 411 and 412 areinsulated from making an electrical connection to each other. At eachintersection of the resistive yarn 420 with one of the electrode yarns411 and 412, the resistive yarn 420 is placed in electrical connectionwith the respective electrode yarn 411 or 412. In this manner, anelectrical circuit is formed having the electrodes 411 and 412interconnected by a series of segments from the resistive yarn 420, thusforming a parallel resistive circuit. The parallel resistive circuit cangenerate heat in a similar manner to the textile 300 by applying anelectrical current between the electrode yarns 411 and 412.Additionally, any break in yarn electrode 411 or 412, will create achange in the electrical potential across the electrode yarns 411 and412, indicating a location of the break. Therefore, a break within thepipe 10 causing a break of one of the electrodes 411 or 412, can belocated by measuring the electronic potential across the electrode yarns411 and 412.

In addition to the textiles 300 and 400 illustrated in FIGS. 5 and 6, atraditional woven or knitted textile having thermal generating elementscan be incorporated as the reinforcing textile 120 illustrated in FIGS.1 and 2. For example, a traditional woven fabric having selvage yarns,pick yarns, and filling yarns, can incorporate the thermal heatingaspects of the textiles 300 and 400. The picks of a traditional wovenfabric can be the resistive elements, and the selvage yards and/or fillyarns can be a conductive material. Alternatively, the fill yarns can beformed of a resistive material, and the pick yarns can be conductiveyarns which are electrically supplied by conductive selvage yarns and/orconductive fill yarns. In yet another embodiment, the resistive yarnscan be a combination of pick and fill yarns.

Referring now to FIG. 7, there is shown an apparatus 500 for the in situformation and placement of an embodiment of the pipe from the presentinvention. The apparatus 500 includes a transportation device 510 suchas a truck, a trench or ditch digging device 520 located on thetransport device 510, and an apparatus for formation of the pipe 530such as the pipe forming apparatus 20 in FIG. 3. A supply of reinforcingtextile 540 (such as a roll of the reinforcing textile 120 in FIG. 1) ispositioned with the transportation device 510 to supply the pipe formingdevice 530 with the necessary reinforcing material 120 to form the pipe10. Additionally, an extruding device 550 with a plastic supply 551 ispositioned with the transportation device 510 for supplying meltedmaterial to the inner wall dye 210 of the pipe forming apparatus 200 forforming the inner wall 110 of the pipe 10. A second extruding device 560with a material supply 561 extrudes material and supplies the materialto the outer wall die 240 of the pipe forming apparatus 530 for formingthe outer wall 130 of the pipe 10. Although the two extruding devices550 and 560 have been illustrated as a separate supply, it iscontemplated that the two extruding devices could be a single extrudingdevice.

Still referring to FIG. 7, the ditch or trench digging device 510removes material from the ground for placement of the pipe 10. Theextruding apparatus 520 receives extruded material from the extrusiondevice 550, reinforcing material 20 from the supply, and extrudedmaterial from the extrusion device 560 for forming the inner wall 110,reinforcing textile 120, and outer wall 130, respectively, of the pipe10. The pipe 10 is positioned within the trench or ditch formed by thetrench or ditch digging device 520 and earth is placed over the pipe 10as necessary. The process is continuous allowing the transportationdevice 510 to form and place the pipe 10 in situ.

Having described the invention in detail it is obvious that one skilledin the art will be able to make variations and modifications theretowithout departing from the scope of the present invention. Accordingly,the scope of the present invention should be determined only by theclaims appended hereto.

1. An apparatus for the in situ formation and placement of atextile-reinforced pipe, said apparatus in combination comprising: atransportation device, on which said transportation device are located atrench forming device, a pipe forming device, a textile reinforcementmaterial supply, and at least one extrusion material device; said pipeforming device having (a) an inner wall die for receiving a first layerof extruded material from the at least one extrusion material device andforming an inner wall, (b) a textile reinforcement material guide forreceiving a textile reinforcement material from the the textilereinforcement material supply and positioning the textile reinforcementmaterial on the inner wall, and (c) an outer wall die for receiving asecond layer of extruded material from the at least one extrusionmaterial device, wherein the textile reinforcement material has an openmesh structure, and wherein said trench forming device and said pipeforming device are positioned such that said pipe forming devicepositions a pipe within a trench formed by said trench forming device.2. The apparatus of claim 1, wherein the textile reinforcement materialhas a construction selected from the group consisting of a knitconstruction, a woven construction, a non-woven construction, and anin-laid construction.
 3. The apparatus of claim 1, wherein the textilereinforcement material has an elongation at break of about 2-3%.